Sedimentary record of Cretaceous and Tertiary salt movement, East Texas basin : Times, rates, and volumes of salt flow and their implications for nuclear waste isolation and petroleum exploration

Post-Aptian strata (younger than 112 ma) in the East Texas Basin were strongly influenced by halokinesis and recorded the evolution associated sate structures. Comparisons with model diapirs and dome-induced changes in patterns of sandstone distribution, depositional facies, and reef growth indicate that thickness variations in strata surrounding domes were caused by syndepositional processes rather than by tectonic distortion. Salt domes in the East Texas Basin exhibit three stages of growth: pillow, diaper, and postdiapir. Each stage affected surrounding strata differently. Pillow growth caused broad uplifting of strata over the crest of the pillows. The resulting topographic swells influenced depositional trends and were susceptible to erosion. Fluvial-channel systems bypassed pillow crests and stacked vertically in primary peripheral sinks on the updip flanks of the pillows. Diapir growth was characterized by expanded sections of shelf and deltaic strata in secondary peripheral sinks around the diapirs. Lower Cretaceous (Aptian stage) reefs on topographic saddles between secondary peripheral sinks now host major oil production at Fairway Field. Postdiapir crestal uplifting and peripheral subsidence affected smaller areas than did equivalent processes that occurred during pillow or diaper stages. Long-term and recent rates of dome growth in East Texas indicate a low probability that future dome uplift will breach an intradomal waste repository. During deposition of the Eocene Wilcox Group, fine-grained floodplain sediments accumulated over and around active diapirs in the East Texas Basin, including Oakwood salt dome. These fine-grained sediments now sheathing diapirs are aquitards favorable for waste isolation. However, sand-rich channel facies in rim synclines commonly surround the fine-grained sheath and constitute interconnected aquifers around diapirs. A potential pathway for radionuclides leaking from a dome could occur if interconnected aquifers intercept the dome. Dome-specific facies variability is difficult to detect because the variability commonly exceeds available well spacing. Site characterization of a potential waste repository must therefore be based on dense well control and on an understanding of dome growth history and diapiric processes in order to better predict facies distributions around domes. Facies variations over and around domes at different stages of growth enable prediction of the location of subtle, facies-controlled hydrocarbon traps. These facies traps are likely to be the only undiscovered traps remaining in mature petroliferous basins such as the East Texas Basin.